Abstract:

Dawa oilfield consists of multi fault blocks of reservoirs. The contents and properties of crude oil vary among different blocks;and the oil maturation increases especially from the deep bed to the shallow for the reason of the variation of the faults in the forming time and in the sealing capacity. The main fault in Dawa oilfield is a long-term active fault, companying with SWW direction faults in Eocene and NWW-EW direction faults in Neocene. Faults in Eocene play a role of petroleum migration pathway from the Es₃ formation,and the fault in Neocene control the petroleum accumulation in Ed formation. The later faults transported much higher maturation petroleum than the early faults because the degree of petroleum maturation in source bed is more and more higher. The episodic release of the abnormal pressure in source rocks also contribute to the different maturations in different beds vertically and different blocks laterally. The occurrence of the oil and gas in different formations also depends on the balance of the migration ability of petroleum from the source rock and the resistance force of the capillary pressure of the reservoir rock.

Key words: fault, accumulation in fault block,  petroleum migration;maturation,  Neocene, Dawa oilfield, Liaohe subbasin